The present invention relates to a data transmission device for hearing aids having a modulatable oscillator circuit for generating an alterable transmission signal and an antenna device for radiating the transmission signal.
Wireless data transmission between hearing aids or between a hearing aid and a remote control unit necessitates that the hearing aid or the hearing aids have a modulatable transmission oscillator which it should be possible to integrate into the respective hearing aid's integrated circuit. For the transmission devices in hearing aids, however, there are very specific constraints. First, there is the small amount of available space, particularly in in-ear hearing aids, and secondly, there is a very small available current for supplying the transmitter, which is usually in the region of microamps. Another constraint is the high frequency stability required for transmission, which can usually be achieved only with a crystal oscillator.
To date, these constraints have been able to be observed only by amplitude-modulated transmitters in hearing aids, so as to ensure, by way of example, “cross” and “bi-cross” transmissions between hearing aids. For the transmitters, popular standard oscillator circuits have been used. A drawback of these standard circuits is the high power consumption and also the use of a relatively voluminous crystal oscillator as the frequency standard.
In this connection, the printed German patent document DE 101 15 896 discloses a hearing aid system having a programmable hearing aid and a transmission and reception unit. For the purpose of wireless programming, the hearing aid is provided with a transmission and reception unit which is detachably connected to the hearing aid. This transmission and reception unit preferably has the external shape of a hearing aid battery and can be inserted into the hearing aid's battery compartment for the purpose of programming. This means that components which are required for wirelessly programming the hearing aid are connected to the hearing aid only during programming. While the hearing aid is being programmed, data are provided in an external programming unit and are transmitted using a transmission and reception coil in the form of electromagnetic waves to a separate transmission and reception coil associated with the hearing aid.